The present disclosure relates generally to ocular implants for IOP control that use a reed valve to regulate drainage.
Glaucoma, a group of eye diseases affecting the retina and optic nerve, is one of the leading causes of blindness worldwide. Most forms of glaucoma result when the intraocular pressure (TOP) increases to pressures above normal for prolonged periods of time. IOP can increase due to high resistance to the drainage of the aqueous humor relative to its production. Left untreated, an elevated IOP causes irreversible damage to the optic nerve and retinal fibers resulting in a progressive, permanent loss of vision.
FIG. 1 is a diagram of the front portion of an eye that helps to explain the processes of glaucoma. In FIG. 1, representations of the lens 10, cornea 20, iris 30, ciliary body 40, trabecular meshwork 50, Schlemm's canal 60, and anterior chamber 70 are pictured. Anatomically, the anterior segment of the eye includes the structures that cause elevated IOP which may lead to glaucoma. Aqueous humor fluid is produced by the ciliary body 40 which lies beneath the iris 30 and adjacent to the lens 10 in the anterior segment of the eye. This aqueous humor washes over the lens 10 and iris 30 and flows to the drainage system located in the angle of the anterior chamber 70. The angle of the anterior chamber 70, which extends circumferentially around the eye, contains structures that allow the aqueous humor to drain. The trabecular meshwork 50 is commonly implicated in glaucoma. The trabecular meshwork 50 extends circumferentially around the anterior chamber 70. The trabecular meshwork 50 seems to act as a filter, limiting the outflow of aqueous humor and providing a back pressure that directly relates to IOP. Schlemm's canal 60 is located beyond the trabecular meshwork 50. Schlemm's canal 60 is fluidically coupled to collector channels (not shown) allowing aqueous humor to flow out of the anterior chamber 70. The two arrows in the anterior segment of FIG. 1 show the flow of aqueous humor from the ciliary bodies 40, over the lens 10, over the iris 30, through the trabecular meshwork 50, and into Schlemm's canal 60 and its collector channels.
One method of treating glaucoma includes implanting a drainage device in a patient's eye. The drainage device allows fluid to flow from the anterior chamber of the eye to a drainage site, relieving pressure in the eye and thus lowering IOP.
Conventional drainage devices are passive valves that have limited control over flow rates and are designed to drain fluid from the anterior chamber to a drainage location elsewhere in the eye. These devices have only limited control over the flow rates of fluid through the device, and are often most effective when pressure differentials between the anterior chamber and the drainage site are relatively small. When pressure differentials are larger, such as during the periods immediately following implantation, the passive drainage device can be ineffective in controlling flow leading to high frequency oscillatory pressures, and also may allow excessive drainage leading to an excessively quick drop in pressure and in IOP, possibly resulting in hemorrhaging or chamber collapse. What is needed is a system that provides stabilized flow control through the drainage device even in high pressure differential scenarios, such as immediately following surgery.
The system and methods disclosed herein overcome one or more of the deficiencies of the prior art.